Jay I think a lot of people forget, you must work for a awesome company, most companies won't let there employees film at work, just a big thanks to your boss, from everyone on here.
Thank You, man! As an engineering student, it's beautiful, when the theory becomes something real and these information you gave are not so common. Thanks!
I had a lot of questions about how the exhaust nozzle works and what it actually does on fighter jets, I watched a lot of videos but this one made it all clear, especially after 5:00 - A big thanks for uploading these videos! Have a great day
I can feel my brain growing while watching your videos!! I have never really understood the inner workings on turbine/jet engines and after watching your videos its all making sense! Thanks so much!
This is the most informative explanation I have ever seen (not that the Wiki and other eLiterature I came across didn't help). It has confirmed to me that my impressions of how the exhaust nozzles work are correct (no misconceptions) Brilliant!
As an A&P student in PowerPlant studies, AgentJayZ’s videos have been an extremely helpful resource! Thank you for caring enough about everyone to show everyone what you do!
I have no engineering knowledge whatsoever, but I really thank you for sharing these videos and introducing the general public to your field. Very interesting.
Everytime I watch your videos I can't help but think about how much time you must put into them (filming, going thru the film, editing, etc) ....All at the expense of the satisfaction of a few thousand viewers. You, Jay, are the epitome of a gearhead! Thanks so much Jay! Also, good news, your username appeared in youtube's search bar a few weeks ago, I think....hoping for an exponential increase in subscribers in the near future. Pretty soon you'll be making the front page of youtube! :)
Thank you so much for this series of vids on Jet engines and Afterburners, Jay. I've always been fascinated with Jets, and love watching and hearing the big military jobbies (my fav is the F111). In principle, they are extremely simple things. In reality, the way all the parts function together is quite complex. As is the metallurgy involved to get them to survive the extreme conditions they operate under. I finally understand the workings or an afterburner - thanks to you. Top stuff, mate.
I stumbled on your videos a couple of weeks ago... Love them all. They have expanded my knowledge of turbines. Would love to have you explain the variable stators sometime. Keep up the excellent work!
That extension and retraction mechanism is beautiful. I used to manufacture prototype film camera lenses and it's a very similar technology to an Iris mechanism, but a little warmer.
the construction and operation of these nozzles has always perplexed me. They seem so simple, yet complicated at the same time lol. It was cool to not have the engine noise drowning out the nozzle sound and actually getting to hear it for once, awesome video and your shooting angles are getting really creative
There is no music in this video... you must be hearing interference between the fluorescent lighting, and a helicopter hovering at the airport, a half mile away.. ...must be that.
Thankyou that was very thoroughly explained AgentJayZ, you're my hero =) Oh Canada our home and native land. Always excited to see new videos from you.
In Thailand, with the 388th TFW, good old MacNamera had his bright idea that all AF specialist, (I was Avionics) would also function as Crew Chiefs. My one and only job as a Crew Chief...making the flame holder inspection on a J-75 (Thud engine). Suited up in a protective suit, my skin covered in protective gloves, just a little skin showing, I climbed up the tail pipe, brushed at each corner of the flame holder, used a dye, then black light, looking for cracks. Climbed out some time later, hot, sweaty, and black as coal. I was glad that the AF brass had better sense than to take highly trained Avionics people and waist them as crew chiefs.
I always like hearing the stories of people who were really there, in the field, using these things for their design purpose. I have a lot of respect for the fliers and the maintainers.
it is so nice to see a video that shows the metal parts working......well done.....I am studying to be an AME and I am becoming a afterburner lover rsrsrsrrsrs
@nhnifong I think it's just to give it some strength so it doesn't ripple and wobble. A bit like the inner layer of corrugated cardboard. Or maybe it's because heatilons are a bit shy, and would rather travel along a groove than out in the open.
I lived my childhood in a place not far from a military aircraft factory, and I remember the howl of the j79 in the F104 at low altitude and slow speed..I saw also f4 phantoms, but they were much scarcer on the ground.
Part 3 - I can't keep myself from saying it ... but... "I love the smell of burnt Jet-A1 in the morning". LoL Thanks again for posting - really enjoying the 'learning by seeing' about something I have been passionate about all my life :)))
Nice vid, always wanted to see this done. The off road buggy folks make a joystick valve for hydraulic steering that would be perfect for this. One time hook up for both directions.
when does the fuel get sprayed out of the fuel bars? the tourch ignitor gets the ab going, and then fuel gets sprayed from the fuel bars right? great vids, i love them all,,,,,,,,,,,
@krbruner Every engine is a unique project for us. Each customer has their own schedule and needs. The customer we were preparing the J79 for changed their plans, and we have other engines being built that will be ready for test. We can't test it without the owners, who want to witness the test, and we can't hold up the other projects. The test stand is a hot piece of real estate.
Many thanks for showing this. In your previous afterburner video's you show how the nozzle shape changes but not what changed it. With the more modern systems that can direct the flow - each of the hydraulic actuators would be on different circuits?, or is there a different set up al together. Again thanks for the great videos. Marc
@HolyTrinityJCTV The turbine is there to extract energy from the combustion gases and transform it into shaft torque. The turbine turns the shaft. The shaft turns the compressor, which compresses the air, which is mixed with fuel and ignited in the combustors. The air heats up, expands, and rushes out past the turbine. It's like a cycle, but it's all happening continuously.
Man that was awesome ! I always wanted so see a close up of the nozzles to see the mechansim work. One last question arises : how are the nozzles actuated and interlinked ? Is there some sort of ring that is pushed and pulled by the four actuators ? Big Thumbs up from Vienna, Austria
how large does an afterburner have to be to positively effect the thrust in an aftermarket scenerio say a weld on or aa transition ring seal hmm which models are most common without afterburners
In keeping up with the news regarding what my country is doing to stomp out the disease that is ISIL, I read that F22's had conducted targeted strikes in Syria. This got me thinking about what a Raptor can do that older airframes, or UAV's cannot. I don't expect that you are an expert in classified technologies, but I would like to know what you can surmise of the Raptors capabilities. What makes a Raptor so much of an advanced aircraft that it would be selected to conduct these missions over a B2, or even your standard Super Hornet? I mean, it appears to be an air superiority fighter. More to something you may be better suited to address: what can you infer about it's propulsive capabilities that makes it unique amongst other airplanes? Just curious to learn more. Thanks Jay!
The liner is perforated and has "cooling air" rushing in through the holes. I don't know how much of a layer this creates, but I don't think it's very big. I would only be guessing to say it's about a quarter inch thick.
It's hard to tell from watching, but I ran the footage at 3X normal speed during nozzle actuation, and at 1X normal when I was talking. I think what you see at 5:54 is the transition from 3X to 1X.
Does that inner sleeve get replaced after so many hours of use? At constant 2500 deg even if titanium it would slowly become fatigued. It looks to be bolted in for easy replacement perhaps in slots to allow non-binding expansion? So the 800 deg pressurized air in the outer jacket, could it be designed that temp to reduce temperature differential between the inner sleeve sides so as to reduce molecular distortion that causes warpage and premature weakening? Secondly it would seem to prevent the outer skin from icing.
I don't understand all the infatuation with titanium. It is never used in the hot section. You don't understand cooling air. Got videos on combustor liners that explain it. Icing? The cooling air at 800 degrees prevents the outer skin from melting.
@experience4064 The smoke produced by the J79 was a problem that was solved in the late 70s with the introduction of the "low-smoke" or "long life" combustor liners. These are the only liners used today in the industrial engines. The F100 is a completely different engine, being a low bypass turbofan. We never see them. As engines become more specialized for aircraft, they become less suitable industrial powerplants. Light and efficient vs powerful and long-term reliable...
Thailand we could see the F-4E's of the 388th, twenty or so miles out, by the black smoke trail left by the engines Twin trails for the F-4's single for the J-75's of the F-105's. Almost count to see how many made it back from a raid up north. Had more F-4D's with the 81st Fighter Wing at RAF Bentwaters / Woodbridge. Late evening, watching F-4's going out on night training missions, burners lit, that pink flame chasing it off the ground. Was pretty to watch. I worked C-130's over there, Air Rescue on Woodbridge.
Hi Jay, thanks for all the videos they're so much better than all the dumbed down crap on TV. I've noticed that there is a gap between the front of the nozzle and the afterburner jetpipe. Is this something to do with the venturi effect pulling in additional air into the increase the mass of the exhaust? Cooling for the nozzle? These were the only things I could think of but it's probably something totally unrelated.
1) - that's a strange way to describe it. 2) - that's a very strange way to describe it 3) - your username, as a statement, is incorrect. It is however, a commonly held mistaken belief.
So there is just one degree of freedom in such a variable geometry convergent-divergent two-part nozzle? The area of the "throat" and the area of the exit can't be adjusted separately? I have a bit of a hard time to understand how this then hangs together with what I read about the convergent-divergent nozzle geometry, used when the exhaust gas flow needs to be (very) supersonic, *and* the afterburner is on. If the nozzle is in the fully open position when the afterburner is on, with no reduced-area throat to speak of, then the nozzle isn't convergent-divergent, is it? What am I missing?
The exhaust gas in the jet pipe, after the AB fuel burning zone, and before the nozzle exit, is subsonic. When it passes through the exit nozzle, it is accelerated to supersonic, and its further expansion once it has left the exit is exploited by the divergent portion. One thing I have recently learned from the manufacturers description of nozzle function of this engine, is that the primary, convergent nozzle is formed by airflow coming through the gap that can be clearly seen in the thumbnail of this video. That means that literally, the convergent portion of the jet nozzle is made of air and invisible in the J79. I found this very interesting. Very good question.
Question. How many times would you cycle it to be sure it works and would you cycle it at full speed before you ship the engine? Would you cycle it with the engine running and in full afterburner before installing it in the airplane?
Once we get all the bugs out and things work perfectly, we take the engine through its full operating range several times before the owner accepts it. Then it is shipped. When I test the Orenda 14, it is run to takeoff power for 3 or 4 minutes. The engine is limited by the manufacturer to 5 minutes at that setting (106%), and a typical takeoff takes less then 2 minutes. There is no guesswork. Everything the engine is designed for and expected to do in the aircraft, it has already done in the test cell before we return it to the owner. This an absolute requirement, skipped only by fools and idiots.
As you pointed out , the hot ( 800o) air that flows through the spacing in the pipe liner for cooling , is that air coming from exhaust or compressor bypass ? Is that air oxygenized for the combustion of AB fuel , because turbine exhaust has no oxygen left . Me puzzled ! One more stupid question If I may ? At what setting of the nozzle do you get the beautiful howl that the J79 produces ? Thanks for keeping these great flicks on here Jayz
+Christina Daly It is the exhaust flow from the basic engine. Your assertion that turbine engine exhaust contains no oxygen is incorrect. In a turbojet engine, only 20 percent of the air that goes in the front is used to combine with fuel to produce heat. There are many other interesting things to know about how gas turbine engines work. My channel is devoted to distributing this information...
How long does does the full test regimen on an engine take? Since mounting and hooking up all the systems of the engines into the test cell seems to take quite some time, what causes the need to pull the engine out and reschedule the testing, where the entire process has to start from scratch..why not just run it through the testing, then case it and store it?
Hi AgentJayZ, had to ask a few question. Firstly, without the afterburner section, the turbojet would only need a convergent nozzle? When the reheat is off the gas axial velocity after leaving the last turbine blade is subsonic? Does is have to be the case, i.e. without reheat is there a limitation on what the max exhaust gas speed can be? In that case the convergent nozzle causes gas velocity to increase, thereby reducing pressure which roughly equals to the outside pressure by the time it exits the nozzle into the atmosphere. Is that right? When the reheat is switched on, the gas speed goes supersonic and therefore you need a 'divergent' nozzle (the bell shape of the rocket engines) to speed up the gas as well as to decrease the pressure. Thats why you need the fully dilated nozzle for maximum thrust.
Another thing is why does the big hi bypass turbofans have that radial aerospike like structure (instead of the tip a small opening through which probably the core/N2 exhaust comes out) mounted through the nozzle while this J79 has none?
The divergent section is not absolutely necessary, but it makes the nozzle more efficient when the flow is supersonic. You can have a fixed nozzle without reheat, and it can be so small that it is choked, meaning the gas is accelerated to sonic velocity. Then you make a lot more noise without making much more thrust. There are some really good articles and books out there about supersonic jet nozzles. Your questions are at the upper limit of what we can deal with here in a text box.
thanks!!! maybe a closer look to the actuating "ring"? for the nozzle.. and, BTW. ever a chance to film the compressor rotor/case assembly [and the hot section as well] and actually building up the sections on the hyd stand in the floor? [carefull of shop kitty!!] thanks to you and all the crew.. really fantastic[canon OWES you BIG time] T
The thrust control comes from throttle modulating fuel into the core engine and/or afterburner. Basically anything above (ground) idle rpm, the nozzle will close to produce thrust. When afterburning where u are just basically dumping a ton of fuel into the tail pipe and igniting it, that nozzle will open again to maintain a turbine backpressure that won't flame out the core engine.
